Polygalacturonase

Polygalacturonase (PG) is an enzyme produced in plants which is involved in the ripening process, and by some bacteria and fungi which is involved in the rotting process. PGs degrades polygalacturonan present in the cell walls of plants by hydrolysis of the glycosidic bonds that link galacturonic acid residues. Polygalacturonan is a significant carbohydrate component of the pectin network that comprises plant cell walls.[1] The activity of the endogenous plant PGs work to soften and sweeten fruit during the ripening process. Similarly, phytopathogens use PGs as a means to weaken the pectin network, so that a host of digestive enzymes can be excreted into the plant host to acquire nutrients.

Contents

Structure

X-ray crystallography has been used to determine the three-dimensional structure of several PGs. Fungal PGs from Collectotrichum lupine[2], Aspergillus aculeatus[3], and Aspergillus niger (PG1[4] and PG2[5]) have been crystallized. The PG from Erwinia carotovora is the crystallized bacterial PG[6]. Because of the significant role PGs play in agriculture and industry, computational molecular modeling has been applied to generate theoretical structures of other important PGs[7]. The experimentally determined crystal structures are used as templates for the computational threading process.

Inhibition

Main article: polygalacturonase inhibitor proteins

Most plants have inhibitor proteins against some PGs. The polygalacturonase inhibitor proteins (PGIPs) are leucine-rich repeat proteins that have been reported to demonstrate both competitive[8] and non-competitive[9] inhibition of PGs. The crystal structure has been determined for one plant PGIP, PGIP2 from Phaseolus vulgaris (bean)[10]. The theoretical structures of other PGIPs have been determined for some other common crops, using PGIP2 as the template[11].

References

  1. ^ Jones, T. M., Anderson, A. J., and Albersheim, P. (1972) Hostpathogen interactions IV, Studies on the polysaccharide-degrading enzymes secreted by Fusarium oxysporum f. sp. lycopersici, Physiol. Plant Pathol. 2, 153-166.
  2. ^ D. Bonivento, D. Pontiggia, A.D. Matteo, J. Fernandez-Recio, G. Salvi, D. Tsernoglou, F. Cervone, G.D. Lorenzo, L. Federic, “Crystal Structure of the Endopolygalacturonase from the Phytopathogenic Fungus Colletotrichum lupini and its Interaction with Polygalacturonase-Inhibiting Proteins”. Proteins, 70, 294, 2008
  3. ^ S.W. Cho, S. Lee, W. Shin, “The X-Ray Structure of Aspergillus aculeatus Polygalacturonase and a Modeled Structure of the Polygalacturonase-Octagalacturonate Complex”. J. Mol. Biol., 311, 863, 2001
  4. ^ G.Van Pouderoyen, H.J. Snijder, J.A. Benen, B.W. Dijkstra, “Structural Insights Into the Processivity of Endopolygalacturonase I from Aspergillus niger”. Febs Lett., 554, 462, 2003
  5. ^ Y. Van Santen, J.A. Benen, K.H. Schroter, K.H. Kalk, S. Armand, J. Visser, B.W. Dijkstra, “1.68-A Crystal Structure of Endopolygalacturonase II from Aspergillus niger and Identification of 3 Active Site Residues by Site-Directed Mutagenesis”. J.Biol.Chem., 274, 30474, 1999
  6. ^ R. Pickersgill, D. Smith, K. Worboys, J. Jenkins, “Crystal Structure of Polygalacturonase from Erwinia carotovora Ssp. carotovora”. J. Biol. Chem., 273, 24660, 1998
  7. ^ http://www.pg-pgip.info
  8. ^ Federici L, Caprari C, Mattei B, Savino C, Di Matteo A, De Lorenzo G, Cervone F, Tsernoglou D. Structural requirements of endopolygalacturonase for the interaction with PGIP (polygalacturonase-inhibiting protein). Proc Natl Acad Sci U S A. 2001 Nov 6;98(23):13425-30.
  9. ^ Daniel King, Carl Bergmann, Ron Orlando, Jacques A. E. Benen, Harry C. M. Kester, and Jaap Visser; “Use of Amide Exchange Mass Spectrometry To Study Conformational Changes within the Endopolygalacturonase II – Polygalacturonic Acid – Polygalacturonase Inhibiting Protein System”, Biochem. 41, 10225-10233, 2002
  10. ^ A. Di Matteo, L. Federici, B. Mattei, G. Salvi, K.A. Johnson, C. Savino, G. De Lorenzo, D. Tsernoglou, F. Cervone, “The Crystal Structure of Polygalacturonase-Inhibiting Protein (Pgip), A Leucine-Rich Repeat Protein Involved in Plant Defense”. Proc. Natl. Acad. Sci. USA, 100, 10124, 2003
  11. ^ http://www.pg-pgip.info

External links